Well in the OT the ONE GOD said " US & OUR " in Gen.1:26 and in the NT scriptures the Father & Son ( Word ) are called God in John 1:1 ; The Holy Spirit being lied to in Acts 5:3 is called God in verse 4! Then we have God the Father calling His Son ( Jesus Christ ) " O God " in Heb.1:8! Then we have the scriptures that Proves the Word ( Pre-Carnate Jesus Christ ) was NOT Created because ALL Creation was Through/By Him as per John 1:1/Col.1:16! So yes indeed the ( FSHS ) mentioned in Matt.28:19 are in FACT those 3 Divine Persons that mak up the ONE GOD ( TRINITY ) in Gen.1:26 that said " US & OUR "! Case closed on your WRONG say so ( man's word - 2 Peter 3:16 ) that the ONE GOD of the Holy scriptures is not a TRINITY *( FSHS )! You remain 100% rebuked as per GOD's inspired say so in 2 Tim.3:16! Case closed!You don't seem to realize that counting "1, 2, 3" won't result in a single 3 person God.
The text isn't referring to a 3 person God; your imagination is doing that.