On further reading, the xsi is a namespace prefix, and if it's missing/undeclared in the XML stream then you might need to remove that prefix from the data. Again, easier to do if you import as nvarchar(max).
You'd have to modify the column data type in the table you're importing into, and probably change the OPENROWSET to use SINGLE_NCLOB or SINGLE_CLOB. Also note that the encoding may say UTF-8 but the file might have unicode characters that don't translate correctly under UTF-8, so again you'll probably want to remove the <?xml> directive.