The Enfield line had aperture sights, but with apertures large enough to acquire targets and see in low-light conditions. The SMLE had a flip-up ladder-type rear sight mounted forward of the chamber; the No. 4 and 5 Enfields of World War II and the early Cold War had aperture sights mounted behind the receiver.
Around 1900 U.S. Army Ordnance and the American arms industry emulated Mauser by favoring cock-on-opening bolt action rifles. The Enfield line was cock-on-closing, which allows a faster rate of fire. From around 1900 until around Pearl Harbor rapid manipulation of the bolt was a major Infantry task taught by NCOs in both the British and U.S. Armies, with the SMLE and M1903 Springfield respectively.
The M1903 Springfield was really more of a target rifle than a combat weapon, its design having been heavily influenced by the competitive shooters in the U.S. Army. The "amber shooting glasses" crowd had taken over firearms design and Infantry tactics in U.S. Army Ordnance -- just take a look at an early-model M1903 and try to figure out what all the settings are for on its rear sight. For a while during the late 1930s the NRA was implacably opposed to the M1 Garand because it challenged the holy icon status that had been gained by the M1903 Springfield.