We as Americans are rich. We are busy. We are built on routines and schedules. So, has that made our faith weak? We might be a part of a church and talk to someone about Jesus. However, that doesn't really prove our faith even one bit. Why is it so difficult to determine those in Christ and those without Christ? I believe there are two reasons.
First, those who are in Christ are not living out their faith or truly desiring to be set apart. They want to love the world just as much as they love God and that is simply idolatry. We should love people because Christ loves us, but we are called to not love the evil things of this world. Those in Christ must not see God has an addition to our lives but a centerpiece that no other person or thing could ever replace. If you are struggling being set apart from Christ, remember Galatians 5:16 which says "Walk by the spirit, and you will not gratify the desires of the flesh". If you are truly a believer, the holy spirit is with you and you may walk by the spirit, but only through Jesus Christ. Pray that you would walk by the spirit and dig into God's word, because the Holy Spirit grabs on to you tighter and tighter the more you are engaged in the Bible.
Second, in America we are hardly ever tested in our faith. We have it extremely easy since we have freedom to say and do as we please when it comes to our faith. A lot of countries do not have it that easy as they will get persecuted for standing up for Christ. Believers in Christ must continuously be in prayer for the Lord to test our faith just as David did in Psalms as well as it says in James 1:2-4: "Consider it all joy, my brethren, when you encounter various trials, knowing that the testing of your faith produces endurance. And let endurance have its perfect result, so that you may be perfect and complete, lacking in nothing." When I have asked the Lord to test my faith, he has answered my prayers and it truly has helped me grow tremendously in my faith. You might not enjoy it, in fact you most likely won't, but it will truly show you where you are with God and it will bring you closer to the feet of Jesus.
I believe American culture has indeed made our faith weak due to the freedoms we have taken advantage of, getting too comfortable in a rich nation and constantly being busy distracting ourselves from the true mission. However, change is possible and it all starts by asking God to test our faith. We can't let our culture dictate our faith in God.