In that case ...

You are transfered at the same level. In many companies, Sr Staff in China === Staff in US. The best you can negotiate for is Sr Staff in your specific situation.

Also, the bonus percentage (not 100% true though) is fixed at all levels below director.

Since you initiated the relocation, you have less negotiation power (you always have some in any situation).

Strategyh I recommend:
Contact HR immediately to ask tons of questions first. Negotiate later -- focus on base salary (try to get Sr Staff).

Welcome to US!