The situation described in my original answer applies to you, except for no tax treaty benefits. As described above, you started counting days of presence on 1 Jan 2018, and if you were present 183 days or more in 2018, you must file as a resident using form 1040. See IRS Pub 519, "Substantial Presence Test." Take note of the warning in the last paragraph of my original answer - on form 1040 you must report your worldwide income, including any income from investments in your home nation or elsewhere. Filing as a resident, you can deduct property tax and mortgage interest on your residence.
