In Napoleons time the bayonet charge was used to try and route the enemy from their position, to turn them making them an easier target. Napoleans army would have fought with Muskets, In the US civil war the introduction of the rifled barrel, like this Springfield, would have improved the accuracy of the shooter and meant that the charging force was at a distinct disadvantage as the stationary defender could pick them off much more effectively. The chance of using a bayonet was limited as you were probably dead before you got close enough to swing. You can see how the men were lined up in long lines in some of the surviving pictures such as the dead at antietam: Once the generals figured this out you began to see troops taking defensive positions behind trees, hills, walls etc.From what I understand both North and South used some tactics gathered from the Native Americans. Is this right?
I haven't heard of this but it could well be true. I think most of the tactics used were pretty close to those of the Napoleonic wars which saw lines of infantry (dressed in bright colours of course, no allowance for camouflage to protect the troops ) firing at one another at short distances. 
Yeah, I could be mistaking what I thought was a Native American strategy with Sherman's "Scorched Earth" strategy in the south. Pretty brutal stuff.
It was, I always drew some similarity between Sherman and Hannibal Barca in the fact that they both operated so far into enemy territory with no supply lines and any loss would have been catastrophic to the entire army. Although I think Sherman had the easier task given that most of the confederate armies were held up elsewhere when he began his march.
Not to mention the introduction of the Gatling gun. It's been written many times that the general staffs of the European militaries would have been well served to study the US civil war in much greater detail than they apparently did. A bayonet charge at Gettysburg? Disaster. A bayonet charge at the Marne? Fucking suicide. Yet they still tried. I guess they felt they had to do something, and the tank wasn't deployed until the latter years of the war.
Yep and WW1 increased the strength of the defense yet again with the introduction of cordite which was a smokeless powder, before that you had all these guys firing and the thick smoke would drop visibility to only a few meters very quickly. In WW1 they could fire repeated volleys with good visibility, the only reasonable response for the attacking army was to burrow below the hail of accurate fire into shallow foxholes that expanded and expanded to become the miles of trenches. That in itself was interesting as in the very early stages the trenches were straight which meant that a small force that managed to take part of the trench could use enfilading fire along the trench and wipeout huge numbers of enemy troops. So after a while they started building these zig zag ones: