Can i go to a US medical school after getting my pre-med degree in St. George's university in Grenada?

You need a bachelors degree (not a pre-med degree) and you must have the pre-med requirements completed ( a med school web site will list them); then you can apply to med school.  Whether you get accepted or not, can't say.

If you have a pre-med degree that should be fine to apply with as long as it is at the same level as a Bachelor's degree in the US. Most med schools in the US require applicants have a Bachelor's degree. You will need something like that along with these classes:

?General Chemistry
?Organic Chemistry
?Physics
?Biology
?Math(calculus)
?English/Humanities
?Biochemistry

Like you said, you also need to do well on the MCAT(aim for a 30R or above), extracurriculars, and experience in the medical field such as volunteering and shadowing physicians. Possibly any research if you're interested in that.

This is what US med school applicants will have completed and it's what you need to compete with them.

Why don't you try St george medical school. It is one of the best med schools in the region and then you can do your rotations and residency in U.S. But, as for your question, I believe you can as long as you have a good GPA, typically 3.3-3.7 range for the schools here and you have taken the MCAT, and you have at least 90 units of college credits including your pre-med requirements
2 semesters general chemistry with lab
2 semester organic chemistry with lab
2 semesters of biology with lab
2 semester of physics with lab
2 semesters English with lab

Good luck