If you get the Fall of the Samuari expansion, you can eventually hire American, British, and French soldiers to fight in your army.
Just be warned that Shogun 2 has a totally different combat system that requires a lot of strategy and thinking, and has a large learning curve. The gun vs sword battles are actually pretty cool. Shogun 2 doesn't have guns and cannons until near the end of a game, but Fall of the Samurai has guns and steamships from the start.
"I just wasted a bullet. Don't waste your life." -Big Boss