By changing the grading scale you HAVE lied. You are attempting to cheat your way into a foreign college with shady ethics. It is not OK.
–Admissions officers are likely to question the A range going down to to 80, especially if it is way out of line with other applications from your country.
–If you do get into a US college and your lie on the application is found out down the road you will likely be dismissed from that college.
–If you graduate a US college and your lie is discovered down the road you could have your diploma rescinded.
College confidential is not here to encourage or give approval to outright lying on an application. What you are doing is 100% unethical.