Don't feel threatened

It's too early to make any conclusion.

You think too much and might make things complicated. Americans are way more simpler than we'd think. A confident and capable person wouldn't be threatened and intimadated.

Focus on your current work including providing training and coach to the new comer. Be open-minded. If you want to move up to a higher position, you have to know how to coach people.

The better you perform, the better you can secure your position.