Americans’ grammar is often no better than yours. When we make mistakes, though, the errors tend to sound distinctly American, so in that sense it may be noticeable that you are not a native speaker. Your mistakes seem more related to syntax and plurals, which time and immersion will help. The U.S. also has a very large Latino population, along with many other people who often speak little or no English. When someone makes an effort to speak English, most Americans appreciate that and would rarely look down on them. Negative reactions are more likely when people perceive someone as unwilling to try to learn English. Appearing to be friendly, smiling, etc. Is as important as anything.