This question first requires a workable, testable definition of "God" & "Christianity." That is my answer.
Would you be open minded enough to possibility that your computer was not made by anyone, but rather just came into existence?
If I took it to the manufacturer & they said that it wasn't one of theirs, I might have to seriously consider this possibility.
But, as John said, the difference is that the process of making a computer is well understood, & there are all manner of things that trace back to the manufacturers--technical support lines, logos, etc. And other things that just indicate that it was made by humans in general, such as the keys being in human languages, or the fairly universal on/off symbol, or even the fact that the screen projects in the visible spectrum.
A tree grows from other trees. Any "original tree" is long since dead. Since no tree alive today was directly created by some other being, why should we assume that this was ever the case, unless we can locate the designer, or some record of it, & verify its claims independently?