Whether one can use his/her shoes / foot-wear / chappels / slippers inside a Church depends upon his/hers relationship with the ONE in the Church and some other factors. Devotees belonging to most other religions keep away their shoes or foot wear when they enter their Places of worship considering them to be holy. But Christians generally have a habit of not removing their shoes. In countries where the climate is very cold it was used in the olden days to protect their feet from cold. It was justified then.
But in countries like India, it is strongly felt that one should enter the House of God with bare feet. In most denominational Churches in Kerala it is maintained strictly.
When we are instructed to enter the office of some officials and doctors without foot-wear, we scrupulously obey it...! Why don't we voluntarily come forward to do it to show our utmost respect to our God and Master???