"I have a few questions about Matthew 19. Why does Jesus rebuke the rich man for calling him good, and then say that there in none good except for God? Also, why does he say that a rich man shall hardly enter the Kingdom of Heaven? Does this mean that rich people cannot go to heaven, and aren't we all rich compared to other countries?", (Question from Diane Beloncik).
Regarding your first question, Jesus knew that this man did not perceive him to be the Messiah. There were only a few individuals who knew who Jesus really was, because God had revealed this thing to them, "He saith unto them, But whom say ye that I am? And Simon Peter answered and said, Thou art the Christ, the Son of the living God. And Jesus answered and said unto him, Blessed art thou, Simon Barjona: for flesh and blood hath not revealed it unto thee, but my Father which is in heaven" (Matthew 16.15-17 KJV bible). So this man approaches Jesus, not as Messiah, but as a religious authority, and within that capacity bestows an improper title upon him, saying, "...Good Master, what good thing shall I do, that I may have eternal life?" (Matthew 19.26 KJV bible). It would be like one of us addressing a religious leader as, "Oh holy reverend...". One should never glorify or exalt a religious leader, but simply offer the respect and decency with which you would want to be treated. If they are really serving God, then flattery would make them uncomfortable anyways, which is why Jesus corrects this one.
Regarding the second question, let's take a closer look at what happens in Matthew 19. A man approaches Christ, and asks him what he must do to obtain eternal life, which is really akin to asking for salvation. Jesus instructs him to obey the written commandments (they are under the written Law at this time), and then says something unusual. He offers the man the opportunity to sell what he has, have treasure in heaven, and come and follow him. There are many so-called once in a lifetime opportunities (such as maybe getting to meet some bozo celebrity), but only one opportunity that really matters, and this man has been given it. Yet, even though Jesus instructs this man on what he must do to be complete, he is not willing to do it, because he can't accept that he has to leave behind his great wealth and possessions in order to follow Christ.
Jesus remarks to his disciples, "...Verily I say unto you, That a rich man shall hardly [or with difficulty] enter into the kingdom of heaven" (Matthew 19.23 KJV bible). The rich man's wealth acts as an impediment to him entering the Kingdom. Having been given the opportunity to partake of eternal life in Christ, his coveting of wealth holds him back. This is why it is difficult for a rich man to enter the kingdom of heaven, because the wealth presents a distraction and a false security that can obstruct one from focusing on the things of God, "For where your treasure is, there will your heart be also" (Luke 12.34 KJV bible). This doesn't mean that rich people have to literally sell of all their worldy possessions in order to follow Christ, because Christ is no longer with us in flesh. A lot of times, the ones who tell you this are only interested in taking your possessions from you. However, in this instance the rich man has to leave behind all his great possessions to join and serve Christ, and he isn't willing to do so.
Then Jesus goes on to say, "And again I say unto you, It is easier for a camel to go through the eye of a needle, than for a rich man to enter into the kingdom of God (Matthew 19.24 KJV bible)". Alot has been made of this statement, and what it is talking about. A common tradition is that "going through the eye of the needle" is an ancient expression that refers to entering a city by its narrow side gate. A camel would have to unload its cargo and crouch down to enter this side port. Makes a nice story, but the problem is that there really isn't any historical evidence to back up the existence of such an expression. Most likely, Jesus simply means what his statement implies; that it is impossible for a rich man to enter the Kingdom of Heaven. This is why his apostles remark, "Who then can be saved?". If the rich are excluded, then what about everyone else, can they be saved? Jesus then goes to the heart of the matter, and speaking of the nature of salvation he says, "...With men this is impossible; but with God all things are possible" (Matthew 19.26 KJV bible). It is not by right, or by effort, but by God's grace alone that one (whether rich or poor) can enter into the Kingdom of God. So whether rich or poor, if you are willing to heed the Saviour's call he will strengthen you so that you can pass through the eye of the needle, and have eternal life in him, "Because strait is the gate, and narrow is the way, which leadeth unto life, and few there be that find it" (Matthew 7.14 KJV bible).
So does the impediment of wealth affect us more, because America is a wealthy nation? I don't know if our increased standard of living can be understood as being great possessions or wealth, as in the case of the rich man. How many of us if we sold everything we had would have that much? American's are very hardworking people, and while we our blessed, many have to work very hard to make ends meet. However, I would say that in all of our lives there are distractions and forms of idolatry that we must struggle against in order to set our minds on the things of God. It is required that we give up these things because they hinder us from following Christ on a spiritual level. This is especially true in our very materialistic and self-indulgent society, "Mortify therefore your members which are upon the earth; fornication, uncleanness, inordinate affection, evil concupiscence, and covetousness, which is idolatry" (Colossians 3.5 KJV bible).